This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The first goal of this project is to determine the SIV-specific cellular and humoral immune responses and virus evolution in breast milk of SIV-infected or SIV-vaccinated rhesus monkeys. The second goal of the project is to determine the magnitude of the vaccine-elicited, SIV-specific immune response in breast milk following systemic vaccination.